docs: def _spawn_producer(f, port, addr='tcp://127.0.0.1'):
      """Start a process that sends results on a PUSH socket.
  
      Parameters
      ----------
      f : callable
          Callable that takes a single argument, a handle
          for a ZeroMQ PUSH socket. Must be picklable.
  
      Returns
      -------
      process : multiprocessing.Process
          The process handle of the created producer process.
  
      """
      process = Process(target=_producer_wrapper, args=(f, port, addr))
      process.start()
      return process